Obesity, particularly the abdominal phenotype, is associated withseveral reproductive disturbances. Whereas mechanisms by whichobesity affect fertility are complex and still not completely understood,an important role appears to be played by the presence of a condition offunctional hyperandrogenism and hyperinsulinaemia, which accompaniesthe insulin-resistant state. In women with the polycystic ovary syndrome,abdominal obesity may be co-responsible for the development ofhyperandrogenism and associated chronic an ovulation, throughmechanisms primarily involving the insulin-mediated overstimulation ofovarian steroidogenesis and decreased sex hormone binding globulinblood concentrations.By these mechanisms, obesity may also favor resistance toclomiphene and gonadotrophin-induced ovulation and reduce outcomesof IVF/ICSI procedures. Due to the beneficial effects of weight loss,lifestyle intervention programmes should represent the first-line approachin the treatment of infertile obese women. Insulin-sensitizing agents mayadd further benefits, particularly if administered in combination withhypocaloric dieting. Therefore, individualized pharmacological support,aimed at favoring weight loss and improving insulin resistance, should bewidely extended in clinical practice in obese infertile patients. This maybe beneficial even during pregnancy, thereby permitting favourablephysiological delivery and healthy babies.